Electric carillon



Nov. 4, 1941. G, w DEMUTH 2,261,346

ELECTRIC cARILLoN Filed May 31, 1940' Stwentor Patented Nov. 4, e;

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ELECTRIC CARILLON Galan W. Demuth, Moorestown, N. J., assigner to RadioCorporation of America, a corporation of Delaware Application May 31,1940, serial No. 338,088

(ci. :i4- 405) 3 Claims.

This invention relates to an electric carillon and particularly to theconstruction of the vibrating bars thereof. Electric carillons have beenconstructed in which a vibrating member or bar is struck by anappropriate mechanism and the vibrations thereof are picked up by anappropriate electromagnetic or electrostatic means, amplified andreproduced through loudspeakers. The greatest difficulty in theconstruction of such devices lies in the pleasing production of belltones.

It is well known that bells are made of many different types and havecorrespondingly dinerent tone qualities. One of the most importantqualities in bells used in a carillon is that they shall have truepitch, or at least an apparently true pitch. In the construction of theconventional type of carillon, this is extremely dimcult due to the factthat the size of the bell determines its fundamental, which can be tunedwith fair accuracy by turning oil appropriate amounts at the properplaces on the bell. One overtone may also be controlled with reasonableaccuracy, but any attempt to control more than one overtone is so likelyto throw the fundamental oil of pitch that it ls rarely attempted.

In the case of these large bells, the investment in the cast bell is sogreat as to necessarily limit the amount of tuning which may beaccomplished without risking the possibility of recasting the bell.'I'he usual form of bell, however, although containing some overtoneswhich are slightly dissonant, does not have a. large number of louddissonant overtones and the problem is correspondingly simplified.

In the case of electric carillons, a relatively small vibrating memberis used and it is accordingly practical to tune theovertones moreclosely as the loss in material in case the vibrating member is tunedtoo sharp and has to be scrapped is considerably less than the laborinvolved in the tuning. 'I'he disadvantage is partly offset by the factthat the vibrating bars ordinarily used in electric carillons have alarge number of dissonant and fairly prominent overtones.

In the method and apparatus of the present invention, I have provided anovel way of getting two overtones of a vibrating bar accurately in tunewith each other, suppressing the dissonant an improved type of vibratingbar for electric musical instruments.

Another object of the invention is to provide a vibrating bar in whichthe fundamental or apparent frequency is produced as a resultant of twoaccurately tuned harmonics thereof without the fundamental being presentas a mode of vibration of the reed.

Another object of the invention is to provide a vibrating bar in whichthe fundamental or apparent frequency is produced as a resultant of twoaccurately tuned harmonics thereof.

Other and incidental objects of the present invention will be apparentto those skilled in the art from consideration of the followingspecification in connection with the accompanying drawing, in whichFigure 1 is an end view of a carillon mechanism showing the strikingmechanism and mounting of one bar with its associated pickup andindicating the presence of additional bars and Figure 2 is a front viewof one of the carillon bars showing the construction thereof.

Referring first to Fig. l, which shows a striking mechanism somewhatanalogous to that described and claimed in my application Serial No.248,542, filed December 30, i938 (RCV docket 6515), appropriate keyssuch as indicated at I0 are provided. 'I'hese keys, when struck, strikean appropriate stop such as a felt strip I I. When the key strikes thestrip I I, the member I 2, which is rigidly connected to the key I0, isso located that the hammer I4 is about an eighth of an inch from thevibratable bar 2li. The hammer H is carried by the spring member I3 andswings forward by its momentum, striking the bar 20 and beingimmediately withdrawn therefrom both by the reaction from .the blow andby the action of the spring I3, thereby preventing any damping of thevibration of the bar 2U by continued contact of the hammer. The hammerIl is preferably made of wood, but may have a small metal insert forstriking the bar if a sharp impact is desired. A massive support memberI5 is provided which should be of sufficient weight so that it will notvibrate appreciably from thereaction of the bars thereagainst. Thisprevents damping of the vibration of the bars by transmission of thevibration to other members of the apparatus.

overtones and producing the fundamental as a Eachbali Securely fastened,Preferably by hard resultant or subjective tone from the accuratelytuned overtones.

One object of the invention is to provide an improved form of musicalinstrument.

soldering, into a metallic block I6. These blocks may be made of steel,for example. and are about one-quarter of an inch wide, that is, in thedirection of the length of the bar, and are of sub- Another object ofthe invention is to provide stantially the shape shown, being ofsumeient thickness to permit the soldering of the bar into a slot in theblock. The blocks i are secured to the massive member Il by appropriatescrews l1. In proper cooperative relation to each of the bars 2l, thereis mounted a magnetic pickup including a winding 22 and a magnetizedcore 13. 'I'he windings of a whole series of these pickups may beconnected together and connected to the input of an appropriateamplifier adapted to operate an appropriate number of loudspeakers.Other appropriate types of pickups, such for example, as anelectrostatic pickup may be used.

The bars 2l are preferably made of piano wire having a diameter of theorder of .045" and are tuned as hereinafter described.

It is an inherent characteristic of a vibrating bar of uniformcross-section, clamped at one end and free over the remainder of itslength, that its vibrating frequencies are as follows from thefundamental to the 11th partial .Y

It willbe noted from the foregoing table that the fifth and sixthpartials indicated as fs and la above are almost related by the ratio of2:3. Notes having frequencies in the proportion of 2 to 3 are quiteusual in musical tones and. if sounded together, give the simulation ofalso producing a fundamental having the proportional frequency of unity.These two overtones of the bar come closer to having such a ratio oftheir frequencies than any of the others and I have found it possible toso modify the bar as to bring these two partials accurately in tune inthe ratio of 2:3. Further, these two partials have an intensity near themaximum of that of all the partials and, therefore, have acorrespondingly great part in producing the apparent tone of the bar.

I find that by grinding a notch such as indicated at 2| in Figs. 1 and 2in the bar, I am able to tune the said fifth and sixth partialsaccurately to the ratio of 2:3. It seems that the grinding of the notchhas the effect of spreading the series of partials given above so as toaccom- `plish the accurate relative tuning of these two partials. Afterthe notch has been ground, further tum'ng is accomplished by grindingoff the lower end of each bar until the proper pitch is secured.

In the following table, the dimensions of a series of reeds over a rangeof two octaves is given for a diameter of .045" and with the notchesground to a radius of three-eighths of an inch and to such a depth thatthe remaining thickness of the bar at the bottom of the notch is .0250"with a tolerance of .0002" either way. The length L given in the tableis the length from the bottom of the supporting block to the end of thereed to which the wires are cut. These lengths will leave, each notevery slightly flat sd that they may be brought accurately into tune bygrinding, as described above. The frequency indicated as 2f may be tunedwith the assistance of an oscillograph, and when this frequency is thenotch Aa little deeper and retuning the bar, but ordinarily it is lessexpensive to discard the bar and substitute a new one of proper dimenqsions.

Tuned frequencies Non 2/ a/ p L 196.00 mo ssao ses 13M 901.65 41s.: m951s 13M moo 440.0 oeao so: 121,4

mos 4cm 099.2 m 1214 m94 49:4.9 14o.s u1 129s.

%1.63 523.3 784.0 M7 111Mo 399.63 ma 988.9 soo 101%:

.1.49.21 was 1041.1 4s4 10% 3&.90 740.0 1110.0 408 91%0 moo 184.0 1116.0.441s 9114.

411:40 me mso .45a 9% 44o seo 1390 4:11 916 406.16 932.3 1a9as 4:1 81A587.3 1174.6 1762.0 4M 71ia was 1318.5 1911.3 :191 114 MAG 1396.0 2195.4.391 7%:

730.90 14&).0 2211.0 .N1 71de It should be noticed that the resultantpitch is not tuned directly and does not appear as a partial of the bar,but it is produced as a difference frequency between the tunedfrequencies 2f and Il. If an oscillograph is connected to the pickupmagnet, it will show'the frequencies tabulated as 2f and as 3f, and itwill also show that the frequency f is not physically present in thevibration of the bar, although the frequency f is the one which isapparent to the ear.

It will be apparent to those skilled in the art that the invention isnot limited to the use of the fth or sixth normal partials of avibrating bar tuned to two and three times the frequency of theresultant note which is to be produced, but that I may use otherpartials of the bar tuned to produce other true harmonics of theapparent fundamental frequencies desired. For

example, the second and third partials might be tuned to the ratio ofone to three; or the third and fourth partials might be tuned in theratio of one to two; or the seventh and eighth partials might be tunedin the ratio of three to four and so on. The selection of these otherpartials would, of course, require a corresponding change in theposition of electrical pickup so as to bring out the particularfrequencies which are desired and suppress others and in some instanceswould also require the design of special amplifiers to suppress theundesired frequencies. In the preferred form of the invention describedabove, the fundamental of the bar, which appears as a relatively strongvibration, lies below the range eectively amplified by commercialamplifiers and is not readily picked up at the position of the pickupdescribed. In general the selection of low partials of the bar rendersthe elimination of the fundamental of the bar difficult and also rendersthe elimination of the dissonant higher harmonics diLcult due to theirhigh amplitude and ready amplification, Likewise, the choice of partialswhich are too high in the series produced by the bar renders dimcult theelimination of dissonant lower partials which fall well within the rangeof audio amplifiers.

The pickup should be located at a position on the bar which is at adistance from the block II of twice the dimension D, as this gives thebest pickup of thev particular frequenciesdesired. The position of thehammer Il is notsoiimportant, .although it. operates. the bestwhen'flocated at approximately the relative position indicated in thedrawing. `If -thehammer is moved much',

closer to the point ofs'upport of the bar,.itrmakes the sound producedmore ,tinkly, while if it is moved much farther dowr'ionthe bar, itproduces point of support the notch mustbe'made morev shallow,Conversely, if the `notch is m'oved far'- ther from the point of supportit must be made deeper. Either of these' changes adds .to the difficultyof production. The bar has a tendency to be slightly. annealed where itis hard soldered into the supporting block and if the notch falls withinthe portion `of the bar` where the vhardness is affected, thedimensionsof the notch will not be uniform but must be adjustedaccording to the hardness of the part thereby requiring a separatetuning operation for the notch. Conversely if the notch is moved fartherdown the bar and is made deeper, the quantity of material remaining inthe bar at the notch becomes less and the tolerances in the dimensionsof the notch become correspondingly more critical.

Byv a comparison of the table with the length of natural frequencies ofa vibrating bar given above, it will also be noted that the fundamentalfrequency of each unnotched bar is 1%66 of the fifth partial, which isgiven as 2f in the table, and the fundamental of the bar is, therefore,not more than 1%83 of the frequency ffwhich is the apparent or resultantfundamental. For example, for the note g having a resultant fundamentalof 196jcycles per second, the fundamental of the bar itself is6.95'cycles per second, which is well below the audiblerange, Even forthe corresponding note tw'o octaves higher, or 783.99 cycles per second,the fundamental of the unnotched bar is only 27.7 cycles per second,which is substantially inaudible, particularly i when theelectromagnetic pickup is located as' above described at a distance fromthe point of J diameterin order` to facilitate tuning. vIf the y supportof only of the lengthof theI bar, and v.this frequency is lowered by thenotch. It will e also be noted thatthe length of-'thevibratable bar' is`in all instances considerably more than 1GO times the diameter'thereof,y VVAlthough this is not -essential vto .the production of thedesired tones, the vbar should'- be long inv relation to itsrespondingly great dificulty in tuning vand greater increase in wastage.

jI claim as my invention: Y 1. Incombination, a vibratable bar ofsubystantially uniform circular cross-section, supstantially uniformcircular cross-section having a length more than one hundred times itsdiameter, supporting means lfor said bar, said bar having an arcuatenotch therein at a distance of approximately one-twentieth of its lengthfrom the supported end thereof, said notch being substantially half Waythrough said bar, means for striking said bar at a predetermined point,and electrical pickup means located at a distance of approximatelyone-tenth of the length of the bar from the supported end thereof.

3. In combination, a vibratable bar of substantially uniform circularcross-section, supporting means for said bar at one end thereof, saidbar having an arcuate notch therein at a distance of the order ofone-twentieth of its length from the supported end thereof, means forstriking said bar at a predetermined point, and electrical pickup meanslocated at a distance of the order of one-tenth of the length of the barfrom the supported end thereof whereby said pickup means will pick uptwo partials of the said bar having a frequency ratio which can beexpressed in small whole numbers.

GALAN W. DEMUTH.

